In general, a circuit breaker operates to engage and disengage a selected electrical circuit from an electrical power supply. The circuit breaker ensures current interruption thereby providing protection to the electrical circuit from continuous over current conditions and high current transients due, for example, to electrical short circuits. Such circuit breakers operate by separating a pair of internal electrical contacts contained within a housing of the circuit breaker. Typically, one electrical contact is stationary while the other is movable. Conventional circuit breakers include a moving electrical contact mounted on an end of a pivotable contact arm, such that the moving electrical contact moves through an arc-shaped motion path. Contact separation between the moving and stationary contacts may occur manually, such as by a person throwing a handle of the circuit breaker. This may engage a trip mechanism, which may be coupled to the contact arm and the moveable contact. Otherwise, the electrical contacts may be separated automatically when an over current or short circuit condition is encountered. This automatic tripping may be accomplished by a tripping mechanism actuated via a thermal overload element (e.g., a bimetal element) or by an actuator element (e.g., an electromagnetic actuator).
Upon contact separation of the electrical contacts by tripping of the circuit breaker, a substantial electrical arc may be formed. It is desirable to extinguish such arc as quickly as possible to avoid damaging internal components of the circuit breaker. However, in previous circuit breakers, although extinguishment of such arcs has been effective, the arc may not have been extinguished as rapidly as desired. Furthermore, more rapid contact separation is desirable.
Accordingly, there is a need for circuit breaker apparatus, circuit breaker contact assemblies, and methods of operating circuit breakers that offer better arc extinguishment following electrical contact separation and/or to promote more rapid electrical contact separation.